A comparative study of hydrophobic silica particle synthesis

•Silica particles were synthesised using NaOH or polyethyleneimine basic catalysts.•A range of silica precursor (TMOMS) concentrations were used.•The spherical particles increased in size with TMOMS concentration.•The particles were hydrophobic without surface modification.•The PEI-silica particles were more hydrophobic than the NaOH-silica particles.

The process to commercially synthesise silica particles with specific properties is a topic of ongoing research since their use in industrial applications including catalysis, coatings and separation materials has dramatically increased in the last decade. Here, silica particles were made using hydrolysed trimethoxymethylsilane (TMOMS) in the presence of either polyethyleneimine or aqueous sodium hydroxide catalysts. This work presents the first in depth study of the effect of TMOMS concentration on silica particles produced by both of these synthetic methods by comparing their size, morphology and chemical structure. The PEI-silica particles were larger in size and greater in yield than the NaOH-silica particles. It was also determined that both species of silica particles are hydrophobic without requiring further surface modification; and that those made with PEI have a higher contact angle, perhaps due to more complete polymerisation. The results demonstrate how relatively facile synthesis routes can wield a high degree of control over the physicochemical properties of silica particles, which is of paramount importance in silica production process intensification.

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